The present invention relates to a battery pack, and to a method of inspecting a storage state of a secondary battery in a battery pack.
A battery pack has been heretofore used for various portable apparatuses such as a mobile phone, a digital still camera, a portable game machine, a notebook personal computer, and an electric power tool. Currently, applications thereof are not limited thereto, and the battery pack has been increasingly used in the fields necessitating a higher output and a higher capacity such as an electric assist bicycle, an electric vehicle, and further, a home electric storage device.
A lithium ion secondary battery is one of the most-mainly-used secondary batteries as secondary batteries built into a battery pack. The lithium ion secondary battery has multiple characteristics as follows. That is, the lithium ion secondary battery is repeatedly usable by charging, has a high voltage output, has high energy density, has little self-discharge, and has a long life. Therefore, the lithium ion secondary battery is used in an extremely-broad range. However, since the lithium ion secondary battery contains a combustible material, adequate care is necessary in handling thereof. Further, for addressing needs of apparatuses such as a higher output and a higher capacity, the number of cases in which secondary batteries (single cells) are multiply-series-connected or multiply-parallel-connected, and are used in a state of a battery pack (assembled battery) is increased, and therefore, more proper handling thereof is desired. Furthermore, in order to determine whether or not a battery pack mounted on an apparatus is safely usable for the apparatus, many battery certification systems for acting certification between an apparatus and a battery pack have been introduced. Accordingly, usage of an inappropriate battery pack is allowed to be restricted by various certification methods including whether or not an appropriate battery pack is used and whether or not an appropriate protection circuit is included.
There is concern that what we call an altered battery pack is manufactured and distributed by disassembling a spent battery pack, to take out a secondary battery, and to build the secondary battery into another battery pack. In such an altered battery pack, undesired over-charge, undesired over-discharge, and/or the like may occur by inappropriately combining secondary batteries, and therefore, a safety issue easily occurs. Therefore, it is strongly desired to appropriately suppress manufacture and distribution of the altered battery pack, for example, by disqualifying such an altered battery pack or substantially disabling a function of the altered battery pack.
A battery pack with an approval function is known from, for example, Japanese Unexamined Patent Application Publication No. 2009-151953. A battery pack (1) disclosed in the foregoing unexamined patent publication is a battery pack having a battery (14) capable of being charged and discharged, and being built into an electronic apparatus (2). The battery pack is characterized in that the battery pack has a certification means (6) that communicates with the electronic apparatus (2) and that implements certification according to a cryptographic algorithm using a code key (8) shared with the electronic apparatus (2). The battery pack is further characterized in that in the case where a remaining battery level detection circuit (10) capable of detecting a remaining level of the battery (14) is included in the battery pack (1), the certification means (6) is mounted in the remaining battery level detection circuit (10) as software or hardware.